Problem: Cookies are on sale! Today each cookie costs $\$0.75$ less than the normal price. Right now if you buy $7$ of them it will only cost you $\$2.80$ ! Write an equation to determine the normal price of each cookie $(c)$. Find the normal price of each cookie. $\$$
Explanation: Let $c$ be the normal price of each cookie. The current price for each cookie is $c-0.75$. The current cost of $7$ cookies is $7(c-0.75)$. Since the current cost of $7$ cookies is $\$2.80$, let's set this equal to $2.8$ : $ 7(c-0.75)=2.8$ Now, let's solve the equation to find the normal price of each cookie $(c)$. $\begin{aligned}7(c-0.75)&=2.8\\&\\ \dfrac{7(c-0.75)}{{7}}&=\dfrac{2.8}{{7}}&&\text{divide both sides by ${7}$}\\ \\ c-0.75&=0.4\\ \\ c-{0.75}{+0.75}&=0.4{+0.75}&&{\text{add }} {0.75} \text{ to both sides}\\ \\ c&=1.15\end{aligned}$ The equation is $7(c-0.75)=2.8$. The normal price of each cookie is $\$1.15$.